textproduct: Rapid City

KEY MESSAGES

- Fog tonight into Friday morning.

- Mild and dry conditions continue through early next week, breezy at times.

UPDATE

Issued at 920 PM MST Thu Nov 12 2026

IR satellite shows low clouds continuing over central SD and the western SD plains north of I-90 through NW SD. Surface obs and area webcams show dense fog has developed across Harding and Butte counties into portions of Meade County. Additionally, fog has moved into parts of Rapid City, mainly east of the Gap. Have issued a Dense Fog Advisory for Butte and Harding counties, the Colony section of Crook County, and the Spearfish foothills. Will continue to expand the advisory through the night as coverage increases. Overnight forecast min temps are too cold across the western SD plains given the cloud cover/fog. Also, max temps tomorrow look too warm across NW/Cntrl SD where clouds are expected to linger into the afternoon. Today's forecast highs were 10-15 degrees too warm in these areas.

DISCUSSION

(This Evening Through Thursday) Issued at 211 PM MST Thu Nov 12 2026

Current upper air models and Water Vapor show ridge axis over the lee side of the rockies, with trough over the Great Lakes, and northwest flow over the region. 21Z surface analysis shows high pressure over southeastern North Dakota this afternoon. Satellite shows lingering fog/stratus stretching from northwest into south central SD. Winds are currently light with temperatures ranging from the upper 30s to near 60.

The fog and low stratus will continue to burn off this afternoon, but is expected to redevelop tonight and continue into Friday morning. Main areas for fog are expected in and around the foothills, but will likely see some patchy fog and stratus over the western SD plains as well. Decent mixing on Friday will bring gusty southeast winds across the region, with the highest gusts (30-40mph) over the plains areas. Similar setup continues on Saturday. Little change with the temperature forecast over the weekend as the overall ridging pattern holds through the weekend. Models show a weak (but dry) shortwave passing through towards the end of the weekend, and we'll see the pattern start to change a bit early next week as the ridge shifts eastward and flattens somewhat. Next chance for any meaningful precipitation returns middle of next week, as long range models show upper trough swinging up from the four corners region into the northern plains. The GFS and ECMWF differ a bit on placement and we're still a week out, so low confidence on location, amount and p-type we might see from this disturbance.

AVIATION

(For the 06Z TAFS Through 06Z Friday Night) Issued At 916 PM MST Thu Nov 12 2026

Fog and low clouds will continue to spread out over much of western South Dakota and parts of northeast Wyoming leading to IFR/LIFR conditions. KRAP will see improvements beginning around 13/18z, returning to VFR conditions. Northwest South Dakota will likely see fog and low clouds for the whole TAF period. Gusty southerly winds across northeast Wyoming will begin to pick up around 13/17z, with max gusts of 30kts possible. Gusty southeasterly winds will begin to develop across western South Dakota starting around 13/15-17z, with max gusts of 35kts possible.

UNR WATCHES/WARNINGS/ADVISORIES

SD...Dense Fog Advisory until 11 AM MST Friday for SDZ001-012-025. WY...Dense Fog Advisory until 11 AM MST Friday for WYZ060.